This project brings together the skills of laboratories at UC-Irvine and at City of Hope Diabetes Research Center to design a new family of dynamic dendronized polymers (denpols) for safe and effective delivery of siRNA into pancreatic islets to suppress the islet cell apoptosis and enhance outcome of islet transplantation. Despite the tremendous potential of RNAi for therapeutics, the lack of safe and effective delivery vehicles hampers the clinical promise of siRNA. While considerable efforts have been directed towards the development of non-viral vectors, few systems have progressed into clinical trials and none has received FDA approval. Based on lessons learned from previous studies, here we propose a novel dynamic denpol system for safe and effective siRNA delivery. The denpol design provides an unprecedented opportunity to combine multivalency and conformational flexibility, precise structural control and combinatorial diversity, and multiple dynamic/responsive features to optimize the effectiveness for siRNA delivery. The preliminary results from the collaboration between the PI and co-I's labs have shown that the denpol system exhibits minimal cytotoxicity and high efficiency in transfecting siRNA into both isolated cells (NIH 3T3) and whole rat islets. Built upon the initial successes, three specific aims are proposed to achieve the overall goal of this study. Aim 1 will focus on the design, synthesis, and characterization of a library of denpols with controlled composition and structure. The molecular parameters for the denpols will be systematically and combinatorial varied for optimization. Aim 2 will investigate siRNA complexation and in vitro transfection to isolated cells (NIH 3T3 and rats INS-1 and mouse NIT-1) for the denpols synthesized in Aim 1, from which the optimal structure/composition with minimal toxicity and optimal transfection efficiency will be determined. Finally, in Aim 3, the promising denpol candidates will be investigated for siRNA transfection by exposing isolated islets in culture as well as through ex vivo perfusion of the rat pancreas to determine the optimal denpols and conditions for safe and effective delivery of anti-BBC3 siRNA into islets to suppress islets apoptosis. Islets are chosen as the disease treatment model to evaluate the proposed denpol vectors for two major reasons: (1) RNAi treatment, such as anti-BBC3 siRNA, has great potential to increase islet yield and improve islet transplantation efficiency. There is an urgent need for safe and effective delivery of siRNA to islets to improve islets transplantation outcome; and (2) Islets should serve as an excellent model system to test in vivo transfection efficiency and safety of our denpols, because like most in vivo tissues, islets are composed of tightly bound cells in an orderly fashion. Successful demonstration of this project will introduce a new generation of synthetic vectors for siRNA delivery and improve the outcome of islets transplantation and help developing treatment for type 1 diabetes.